Android Sensors. Mobile Applica1ons Jay Urbain, Ph.D. Credits:

Transcription

1 Android Sensors Credits: Mobile Applica1ons Jay Urbain, Ph.D. Meier, Reto, Professional Android 4 Applica1on Development. hbp://developer.android.com/guide/topics/sensors/sensors_overview.html hbp://developer.android.com/guide/topics/sensors/sensors_overview.html

2 Objec1ves Sensors Using the Sensor Manager Introduce the available sensor types Finding a device's natural orienta1on Remapping a device's orienta1on reference frame Monitoring sensors and interpre1ng sensor values Using sensors to monitor a device's movement and orienta1on Note included: Using sensors to monitor a device's environment

3 Sensors Sensors that detect physical and environmental proper1es offer an avenue for innova1ons that enhance the user experience of mobile applica1ons. Rich array of sensor hardware in modern devices provides new possibili1es for user interac1on and applica1on development: augmented reality movement- based input environmental customiza1ons

4 Android sensor framework Determine which sensors are available on a device. Determine an individual sensor's capabili1es, such as its maximum range, manufacturer, power requirements, and resolu1on. Acquire raw sensor data and define the minimum rate at which you acquire sensor data. Register and unregister sensor event listeners that monitor sensor changes.

5 Sensor Type Descrip.on Common Uses TYPE_ACCELEROMETER Hardware Measures the accelera1on force in m/s Sensor 2 that is applied to a device on all three physical axes (x, class TYPE_AMBIENT_TEMPERATU RE y, and z), including the force of gravity. Mo1on detec1on (shake, 1lt, etc.). Hardware Measures the ambient room temperature in degrees Celsius ( C). See note below. Monitoring air temperatures. TYPE_GRAVITY SoYware or Hardware Measures the force of gravity in m/s 2 that is applied to a device on all three physical axes (x, y, Mo1on detec1on (shake, 1lt, etc.). z). Interact with sensors using Sensor objects that describe the z). proper1es of the hardware sensor they represent: type, name, manufacturer, accuracy and range. TYPE_GYROSCOPE Hardware Measures a device's rate of rota1on in rad/s around each of the three physical axes (x, y, and Rota1on detec1on (spin, turn, etc.). TYPE_LIGHT Hardware Measures the ambient light level (illumina1on) in lx. Controlling screen brightness. TYPE_LINEAR_ACCELERATION SoYware or Hardware Measures the accelera1on force in m/s 2 that is applied to a device on all three physical axes (x, Monitoring accelera1on along a single y, and z), excluding the force of gravity. axis. TYPE_MAGNETIC_FIELD Hardware Measures the ambient geomagne1c field for all three physical axes (x, y, z) in μt. Crea1ng a compass. TYPE_ORIENTATION SoYware Measures degrees of rota1on that a device makes around all three physical axes (x, y, z). As of API level 3 you can obtain the inclina1on matrix and rota1on matrix for a device by using the gravity sensor and the geomagne1c field sensor in conjunc1on with the getrota1onmatrix() method. Determining device posi1on. TYPE_PRESSURE Hardware Measures the ambient air pressure in hpa or mbar. Monitoring air pressure changes. TYPE_PROXIMITY Hardware Measures the proximity of an object in cm rela1ve to the view screen of a device. This sensor is typically used to determine whether a handset is being held up to a person's ear. Phone posi1on during a call. TYPE_RELATIVE_HUMIDITY Hardware Measures the rela1ve ambient humidity in percent (%). Monitoring dewpoint, absolute, and rela1ve humidity. TYPE_ROTATION_VECTOR SoYware or Hardware Measures the orienta1on of a device by providing the three elements of the device's rota1on vector. Mo1on detec1on and rota1on detec1on. TYPE_TEMPERATURE Hardware Measures the temperature of the device in degrees Celsius ( C). This sensor implementa1on Monitoring temperatures. varies across devices and this sensor was replaced with the TYPE_AMBIENT_TEMPERATURE sensor in API Level 14 hbp://developer.android.com/guide/topics/sensors/sensors_overview.html

6 SensorManager & Sensor class Sensor Manager Used to manage the sensor hardware available on Android devices. String service_name = Context.SENSOR_SERVICE; SensorManager sensormanager = (SensorManager) getsystemservice( service_name ); Sensor Interact with sensors using Sensor objects that describe proper1es of the HW sensor they represent: type, name, manufacturer, accuracy and range. SensorEvent System uses this class to create a sensor event object. Provides informa1on about a sensor: raw sensor data, the type of sensor, accuracy of the data, and 1mestamp. SensorEventListener Interface to create two callback methods that receive no1fica1ons (sensor events) when sensor values change or when sensor accuracy changes.

7 Sensor APIs used for 2 basic tasks Iden1fying sensors and sensor capabili1es Iden1fy all of the sensors that are present on a device and disable any applica1on features that rely on sensors that are not present. Iden1fy all of the sensors of a given type so you can choose the sensor implementa1on that has the op1mum performance for your applica1on. Monitor sensor events Monitoring sensor events to acquire raw sensor data. A sensor event occurs every 1me a sensor detects a change in the parameters it is measuring. Provides four pieces of informa1on: the name of the sensor that triggered the event, the 1mestamp for the event, the accuracy of the event, and the raw sensor data that triggered the event.

8 Accessing a device s sensors private SensorManager msensormanager; msensormanager = (SensorManager) getsystemservice(context.sensor_service); List<Sensor> devicesensors = msensormanager.getsensorlist(sensor.type_all); StringBuffer sb = new StringBuffer(); for( Sensor sensor : devicesensors ) { sb.append( sensor.getname() + "\n"); } Toast.makeText(this, sb.tostring(),toast.length_long).show();

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10 Sensor To find a list of all the available Sensors of a par1cular type: List < Sensor > gyroscopes = sensormanager.getsensorlist( Sensor.TYPE_GYROSCOPE); Each Sensor reports its name, power use, minimum delay latency, maximum range, resolu1on, and vendor type. Hardware Sensor implementa1ons are returned at the top of the list, with virtual corrected implementa1ons last.

11 Do determine if a specific sensor is available private SensorManager msensormanager;... msensormanager = (SensorManager) getsystemservice(context.sensor_service); if (msensormanager.getdefaultsensor(sensor.type_magnetic_field)!= null){ // Success! There's a magnetometer. } else { } // Failure! No magnetometer.

12 Monitoring Sensors Sensors can be monitored by implemen1ng a SensorEventListener:

13 SensorEvent parameter SensorEvent parameter in the onsensorchanged method includes: sensor object - that triggered the event. accuracy The accuracy of the Sensor when the event occurred (low, medium, high, or unreliable). values A float array that contains the new value(s) observed.

14 Accuracy: Sensor Accuracy SensorManager.SENSOR_STATUS_ACCURACY_LOW Indicates that the Sensor is repor1ng with low accuracy and needs to be calibrated. SensorManager.SENSOR_STATUS_ACCURACY_MEDIUM Indicates that the Sensor data is of average accuracy and that calibra1on might improve the accuracy of the reported results. SensorManager.SENSOR_STATUS_ACCURACY_HIGH Indicates that the Sensor is repor1ng with the highest possible accuracy SensorManager.SENSOR_STATUS_UNRELIABLE Indicates that the Sensor data is unreliable, meaning that either calibra1on is required or readings are not currently possible.

15 onresume() & on Pause() Note: system will not disable sensors automa=cally when the screen turns off. public class SensorAc.vity extends Ac.vity, implements SensorEventListener { private final SensorManager msensormanager; private final Sensor maccelerometer; } public SensorAc1vity() { msensormanager = (SensorManager)getSystemService(SENSOR_SERVICE); maccelerometer = msensormanager.getdefaultsensor(sensor.type_accelerometer); } protected void onresume() { super.onresume(); msensormanager.registerlistener(this, maccelerometer, SensorManager.SENSOR_DELAY_NORMAL); } protected void onpause() { super.onpause(); msensormanager.unregisterlistener(this); } public void onaccuracychanged(sensor sensor, int accuracy) { // do something } public void onsensorchanged(sensorevent event) { }

16 Device Movement & Orienta1on Accelerometers, gravity sensors, and gyroscopes offer the ability to provide func1onality based on direc1on, orienta1on, and movement. Example: compass Determine device orienta1on React to changes in orienta1on React to movement or accelera1on Understand which direc1on the user is facing Monitor gestures based on movement, rota1on, or accelera1on

17 Applica1ons Compass to determine heading and orienta1on for use with a map, camera, and loca1on- based services for augmented reality UIs that overlay loca1on data with camera feed. Create UI s that adjust dynamically as the orienta1on of the device changes. UI controls for physical gestures and movement as input.

18 Determine Natural Orienta1on 0 s on all 3 axes typically flat with top of the device poin1ng North. Sensor values are returned rela1ve to the natural orienta1on of the device. May need to adjust sensor input to current display orienta1on.

19 Accelerometers How quickly the velocity of the device is changing in a given direc1on (m/s 2 ) Integrate accelera1on over 1me to get velocity. Integrate accelera1on twice to get posi1on but its too noisy to be useful. Use with gravity to determine orienta1on.

20 Gravita1onal Force Meter

21 Gravita1onal Force Meter

22 Gravita1onal Force Meter

23 Orienta1on Typically calculate orienta1on using combined output of both magne1c field Sensors (electronic compass), and the accelerometers (pitch and roll) on all 3 axes.

24 Define listeners to monitor the accelerometer and magnetometer

25 Register accelerometer and magnetometer

26 Calculate current orienta1on 1 radian = degrees sta1c boolean getrota1onmatrix(float[] R, float[] I, float[] gravity, float[] geomagne1c) Computes the inclina1on matrix I as well as the rota1on matrix R transforming a vector from the device coordinate system to the world's coordinate system which is defined as a direct orthonormal basis.

27 Remap orienta1on to display

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29 Ball Demo